Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$74.67	4.609%	$78.1115	$78.11	$78.10	$78.10
Purchase #2	$150.57	8.143%	$162.8309	$162.83	$162.85	$162.80
Purchase #3	$154.29	4.165%	$160.7162	$160.72	$160.70	$160.70
Purchase #4	$82.91	7.779%	$89.3596	$89.36	$89.35	$89.40
Purchase #5	$209.48	3.801%	$217.4423	$217.44	$217.45	$217.40
Purchase #6	$234.37	9.812%	$257.3664	$257.37	$257.35	$257.40
Purchase #7	$192.88	13.447%	$218.8166	$218.82	$218.80	$218.80
7 purchase totals =	$1,099.17		$1,184.6435	$1,184.65	$1,184.60	$1,184.60